Effect of Unsaturation and Chain Length of Methyl Esters on the Corrosion Behavior of Aluminum

In the present research work, the corrosion behaviour of pure Al in methyl esters with different degree of unsaturation and chain length, present in biodiesel, has been investigated by using electrochemical techniques. Evaluated methyl esters included methyl acrylate (C4H6O2) and methyl linoleate (C19H34O2) which were added to methyl propionate, (C4H8O2) and methyl oleate (C19H36O2 ) respectively. Electrochemical techniques involved electrochemical impedance spectroscopy and electrochemical noise, and were supplemented by detailed studies of scanning electronic microscopy. Results have shown that the corrosion rate and the susceptibility to localized type of corrosion such as pitting increased with an increase in the number of unsaturations and in the chain length. Corrosion process was under charge transfer and was not affected neither by an increase in the number of unsaturations nor in the chain length. The charge transfer resistance value decreased by an increase in the number of unsaturations nor in the chain length.